Automatic transmissions generally include at least one planetary gear set and a plurality of shift elements. The shift elements selectively engage components of the planetary gear sets in order to hinder or prevent rotation of the components. Selective actuation of the shift elements adjusts the gear ratio of the automatic transmission and shifts the automatic transmission between its various gears.
Proper actuation of the shift elements provides smooth shifting between gears and improves performance of the automatic transmission. Thus, shift elements preferably adjust between engaged states and disengaged states in a reliable manner. However, shift elements can fail to adjust between the engaged and disengaged states for a variety of reasons. For example, splines of a shifting element may lock together and hold the shifting element in the engaged state.
If a shift elements sticks or does not operate properly, performance of the automatic transmission can be negatively affected. For example, if a shift element sticks in an engaged configuration, the automatic transmission can be overdetermined in gears that do not require the shift element. However, detecting proper actuation of the shift elements in order to avoid overdetermining the automatic transmission can be difficult or expensive. For example, adding an additional sensor to the automatic transmission can increase a cost and manufacturing time of the automatic transmission.
Accordingly, a method for detecting a nonoperational or malfunctioning shift element in an automatic transmission would be useful. In particular, a method for detecting a nonoperational or malfunctioning shift element in an automatic transmission that does not require a dedicated sensor for each shifting element of the automatic transmission would be useful. In addition, a method for detecting a nonoperational or malfunctioning shift element in an automatic transmission that also includes steps for operating the automatic transmission if the shift element is nonoperational or malfunctioning would be useful.